Hedgehog Signaling Pathway Is a New Target of Cancer Stem Cell Therapy for Breast Cancer Patients.

Abstract

Abstract Introduction: Hedgehog (Hh) signaling pathway is crucial for growth and patterning during embryonic development. We have shown that Hh pathway is constitutively reactivated in human breast cancer (Kubo M et al. Cancer Res 2004). Recently, it has been proposed that only a small subset, termed cancer stem cells (CSCs), posseses tumorigenicity. And, several investigations suggest contributions of morphogenesis pathways including Hh pathway in the maintenance of CSCs. Purpose of this study is to reveal an essential role of Hh pathway in the maintenance of CSCs, and also to reveal a possibility of Hh pathway as a target of CSCs therapy for breast cancer patients.Materials and Methods: A human breast cancer cell line MCF-7 was used. In the present study, we estimated CD44+CD24-/low cells or side population (SP) cells as CSCs. Flow cytometric analysis and sorting were performed to detect and collect CSCs, respectively. To confirm the high tumorigenicity of CSCs, we used a MCF-7 cell xenograft mouse model in NOD/SCID mice. To assess the expression of Hh pathway-related molecules, real-time RT-PCR and fluorescent immunostaining were performed. For blockade of Hh pathway, a Hh inhibitor, cyclopamine, and small interference RNA (si-RNA) against Gli1, a trans-activator of the Hh pathway, were used. We also synthesized peptides with specific affinity for a transmembrane receptor Patched1 (Ptch1).Results: CD44+CD24-/low cells and SP cells in total MCF-7 cells were 10-25% and 1-4%, respectively and these two populations were overlapped with each other. These CSCs were highly tumorigenic, and resistant to anticancer drugs including taxanes.Hh pathway-related molecules such as Shh, a ligand of Hh pathway, and Gli1 were predominantly expressed in CSCs. Cyclopamine and Ptch1 affinitive peptides could suppress the tumorigenicity of CSCs in NOD/SCID mice xenograft transplantation model.Conclusions: Hh pathway at least partly contributes to the maintenance of CSCs in MCF-7 cells. Thus, Hh pathway may be a valuable therapeutic target for CSCs therapy for breast cancer patients. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 1161.